Analysis of differential gene expression between chronic hepatitis B patients and asymptomatic hepatitis B carriers

p53 suppresses hyper-recombination by modulating BRCA1 function

Both p53 and BRCA1 are tumor suppressors and are involved in a number of cellular processes including cell cycle arrest, apoptosis, transcriptional regulation, and DNA damage repair. Some studies have suggested that the association of BRCA1 and p53 is required for transcriptional regulation of genes involved in cell replication and DNA repair pathways. However, the relationship between the two proteins in molecular mechanisms of DNA repair is still not clear. Therefore, we sought to determine whether there is a functional link between p53 and BRCA1 in DNA repair. Firstly, using a plasmid recombination substrate, pDR-GFP, integrated into the genome of breast cancer cell line MCF7, we have demonstrated that p53 suppressed Rad51-mediated hyper-recombinational repair by two independent cell models of HPV-E6 induced p53 inactivation and p53 knockdown assay. Our study further indicated that p53 mediated homologous recombination (HR) through inhibiting BRCA1 over-function via mechanism of transcription regulation in response to DNA repair. Since it was found p53 and BRCA1 existed in a protein complex, indicating both proteins may be associated at post-transcriptional level. Moreover, defective p53-induced hyper-recombination was associated with cell radioresistance and chromosomal stability, strongly supporting the involvement of p53 in the inhibition of hyper-recombination, which led to genetic stability and cellular function in response to DNA damage. In addition, it was found that p53 loss rescued BRCA1 deficiency via recovering HR and chromosomal stability, suggesting that p53 is also involved in the HR-inhibition independently of BRCA1. Thus, our data indicated that p53 was involved in inhibiting recombination by both BRCA1-dependent and -independent mechanisms, and there is a functional link between p53-suppression and BRCA1-promotion in regulation of HR activity at transcription level and possible post-transcription level.

Studying the association of microRNA-210 level with chronic hepatitis B progression

We studied the relationship between hypoxia and microRNA-210 (miR-210) levels, the miR-210 levels in patients with hepatitis B and the roles of miR-210 in liver inflammation. We used the concanavalin A (Con A) murine hepatitis model and inflammation, hypoxia and miR-210 levels were examined. In these patients, we studied serum miR-210 levels and clinical indexes related to hepatitis in 90 patients with different stages of chronic hepatitis B and 30 controls. Two functional assays of miR-210 in vitro under hypoxic condition were conducted. The animal experiments indicated that the liver and serum miR-210 levels significantly increased with liver hypoxia and inflammation. In humans, serum miR-210 levels enhanced with hepatitis severity and were related to serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TB) and prothrombin activity (PTA) levels. The miR-210 functional assays showed that miR-210 elevation might be related to the decreases in HepG2.2.15 cell dehydrogenase activity and HBV replication under hypoxic conditions. Because the liver inflammation causes liver hypoxia which also results in liver and serum miR-210 level elevation, the serum miR-210 level may serve as a molecular biomarker for the severity of hepatitis and increases in liver miR-210 that we see may be a response of hepatocytes to hypoxia during hepatitis progression.

Impact of asymptomatic nodavirus carrier state and intraperitoneal viral mimic injection on brain transcript expression in Atlantic cod (Gadus morhua)

Nodaviruses and other RNA viruses have a profoundly negative impact on the global aquaculture industry. Nodaviruses target nervous tissue causing viral nervous necrosis, a disease characterized by neurological damage, swimming abnormalities, and morbidity. This study used functional genomic techniques to study the Atlantic cod (Gadus morhua) brain transcript expression responses to asymptomatic high nodavirus carrier state and intraperitoneal injection of polyriboinosinic polyribocytidylic acid (pIC). Reciprocal suppression subtractive hybridization (SSH) cDNA libraries enriched for virus-responsive brain transcripts were constructed and characterized. We generated 1,938 expressed sequence tags (ESTs) from a forward brain SSH library (enriched for transcripts upregulated by nodavirus and/or pIC) and 1,980 ESTs from a reverse brain SSH library (enriched for transcripts downregulated by nodavirus and/or pIC). To examine the effect of nodavirus carrier state on individual brain gene expression in asymptomatic cod, 27 transcripts of interest were selected for quantitative reverse transcription-polymerase chain reaction (QPCR) studies. Transcripts found to be >10-fold upregulated in individuals with a high nodavirus carrier state relative to those in a no/low nodavirus carrier state were identified as ISG15, IL8, DHX58 (alias LGP2), ZNFX1, RSAD2 (alias viperin), and SACS (sacsin, alias spastic ataxia of Charlevoix-Saguenay). These and other SSH-identified transcripts were also found by QPCR to be significantly (P < 0.05) upregulated by pIC compared with saline-injected controls within 72 h of injection. Several transcripts identified in the reverse SSH library, including two putative ubiquitination pathway members (HERC4 and SUMO2), were found to be significantly (P < 0.05) downregulated in individuals with a high nodavirus carrier state. Our data shows that Atlantic cod brains have a strong interferon pathway response to asymptomatic high nodavirus carrier state and that many interferon pathway and other immune relevant transcripts are significantly induced in brain by both nodavirus and pIC.

Circulating Th17 cells frequency is associated with the disease progression in HBV infected patients

BACKGROUND AND AIMS

Th17 cells have been shown to mediate host defensive mechanisms in various infections, but their role in HBV infection in humans has not been well characterized. In this study, we analyzed the frequency and cytokines secretion of circulating Th17 cells in HBV infected patients with different statuses, and also evaluated the potential association of Th17 frequency with the levels of liver injury.

METHODS

The study population consisted of 133 subjects, including 40 mild chronic hepatitis B (CHB) patients, 37 severe CHB patients, 20 acute hepatitis B (AHB) patients and 36 healthy controls. The frequency of circulating Th17 cells were carried out by intracellular cytokine staining analysis and serum IL-10 levels were measured by ELISA.

RESULTS

Our data shown that AHB and severe CHB patients had a significant increase of Th17 cells frequency in peripheral blood compared with mild CHB patients and healthy control (both P < 0.05). The elevated prevalence of Th17 cells is positively associated with the increased serum ALT levels in severe CHB patients (r= 0.457, P= 0.004) but had no correlation with serum HBV DNA load. In addition, the serum IL-10 were negatively correlated with the frequency of Th17 cells in PBMC from patients with chronic HBV infection (r=-0.452, P < 0.01).

CONCLUSION

Th17 cells may contribute to the disease progression and pathogenesis of liver injury in HBV infected patients, and the induction of IL-10 may be one mechanism of constraining pro-inflammatory Th17 responses.

Inhibition of STAT1 methylation is involved in the resistance of hepatitis B virus to Interferon alpha

As a major therapy for hepatitis B virus (HBV) infection, Interferon alpha (IFN-alpha) triggers intracellular signal transduction including JAK-STAT pathway to produce various antiviral effector mechanisms. However, patients with chronic hepatitis B usually show low response to IFN-alpha treatment and the underlying mechanism remains unclear. In the present study, HepG2 and HepG2.2.15 cells were used to examine the Type I IFN receptors expression, phosphorylation and methylation of STAT1. STAT1-PIAS1 interaction in cells was tested by protein co-immunoprecipitation. The potential improvement of S-adenosylmethionine (SAM) in the antiviral effect of IFN-alpha was also investigated. Our data demonstrated that both chains of the Type I IFN receptors were expressed for a much higher extent in HepG2.2.15 cells than in HepG2 cells. HBV inhibited dramatically the methylation rather than the phosphorylation of STAT1, which was consistent with an increased STAT1-PIAS1 interaction. Combined with IFN-alpha, SAM treatment effectively improved STAT1 methylation and attenuated STAT1-PIAS1 binding, followed by increased PKR and 2',5'-OAS mRNA expression, thus significantly reducing the HBsAg, HBeAg protein levels and HBV DNA load in the supernatant of HepG2.2.15 cells. Less STAT1 methylation and subsequent increased STAT1-PIAS1 interaction are involved in the mechanism of the IFN-alpha-antagonistic activity of HBV. By improving STAT1 methylation, SAM can enhance the antiviral effect of IFN-alpha.